In recent years, obesity due to overeating, shortage of exercise and the like, particularly lifestyle-related disease accompanying accumulation of visceral fat, has become a social problem. Metabolic syndrome refers to a condition where at least two of hyperglycemia, hypertension and lipid abnormality are complicated and arteriosclerosis is easily developed due to visceral fat obesity. In Japanese people at the age of 40-74, one in two in male and one in five in female are estimated to have or potentially have metabolic syndrome. Therefore, the importance of adjustment of ingestion calorie by diet therapy with the aim of preventing or solving progress of lipid accumulation in metabolic syndrome has been proposed.
There is considerable interest in ingestion, in dining, of functional lipids reported to have a lipid metabolism improving effect, a diabetes improving effect and the like, including conjugated fatty acids such as conjugated linoleic acid and the like (non-patent document 1), ω3 polyunsaturated fatty acids such as eicosapentaenoic acid, docosahexaenoic acid and the like (patent document 1), medium chain fatty acid (patent document 2) and the like.
In addition, it has been reported in recent years that a part of oxo fatty acids such as 9-oxo-octadecadienoic acid, 13-oxo-octadecadienoic acid and the like contained in tomato have an activity to improve lifestyle-related diseases, such as lipid metabolism improvement and the like (patent document 3, non-patent documents 2, 3). Therefore, the physiological functions of rare fatty acids such as oxo fatty acid, hydroxy fatty acid and the like are also drawing attention.
As regards production of rare fatty acids such as oxo fatty acid, hydroxylated fatty acid and the like, a production method of C10-position hydroxylated fatty acid and C10-position oxo fatty acid, each having 18 carbon atoms, which uses hydration dehydrase derived from Lactobacillus plantarum, and which was found by the inventors, has been reported (patent document 4). In addition, a metabolism improving effect (patent document 5), and an intestine protective action (patent document 6) relating to these C10-position hydroxylated fatty acid and C10-position oxo fatty acid have also been reported. However, no report exists as to a suitable production method of hydroxylated fatty acid and oxo fatty acid, each having a carbon atom number other than 18 or hydroxylated fatty acid and oxo fatty acid, each having hydroxyl group, carbonyl group at a position other than C10-position. Moreover, physiological functions of these rare fatty acid derivatives are also unknown.